The present invention relates to fluid flow machines in general, and more particularly to improvements in diaphragm pumps. Still more particularly, the invention relates to improvements in diaphragm pumps which are designed to convey flammable gaseous, hydraulic or otherwise flowable media.
It is already known to induce the flow of a flammable medium by resorting to a diaphragm pump wherein the marginal portion of the diaphragm is clamped in the pump housing and divides the interior of the housing into a pumping chamber and a second chamber. The second chamber receives parts of the mechanism which serves to deform the diaphragm so as to alternately increase and reduce the volume of the pumping chamber, i.e., to induce the flow of a medium into the pumping chamber when the volume of the pumping chamber is on the increase and to effect expulsion of a metered quantity of such medium from the pumping chamber when the volume of the pumping chamber is on the decrease. As a rule, the second chamber communicates with the surrounding atmosphere. Reference may be had to German Pat. No. 23 22 764 which discloses a diaphragm pump of the just outlined character. A drawback of the patented pump is that it cannot be used in installations where the penetration of burning media into the atmosphere can result in fires, explosions or similar disasters. This is due to the fact that, once the diaphragm is destroyed or dislodged so that it allows a flammable medium to flow from the pumping chamber into the second chamber, ignition of the medium in the second chamber can propagate itself into the surrounding atmosphere practically without any obstruction. A first explosion in the second chamber triggers a secondary or follow-up explosion in the surrounding atmosphere. Therefore, the usefulness of the patented diaphragm pump is rather limited because it cannot be put to use under circumstances when the propagation of flames or sparks from the second chamber of the pump housing can or is likely to initiate an explosion in the area around the pump.